[Richard]

Any 52" long spring will work. Even rears from a 67-72. Length is measured along the arch on spring, not in a straight plane. Some have confusion regarding lift after conversion. The conversion brackets provide no lift, unless going to a longer than 4" shackle. Stock rear springs have more arch than the fronts so the conversion typically nets 4"-5" of lift depending on spring and shackle used. IMO an old pair of rears will probably net better results than a new pair of rears. Unless going with new from Deaver, Alcan or Atlas. A bit pricy, but you could also have springs made with less lift if you want.